Goldfish are very dirty fish producing lots of excreta (invisible to us, it is in solution and is mainly ammonia). The solids are not a problem (except it makes the water murky), it is the invisible ammonia, equivalent to our urine, that will eventually kill the fish.
This ammonia has to be diluted. This means say five Goldfish would need at least
a 36"x15"x12" aquarium, preferably a 48" if the Goldfish are large, to give enough
water to dilute this excreta. The traditional 'Goldfish bowl' is quite unsuitable,
even one Goldfish needs an 18" tank. In a small volume of water the ammonia builds
up and self-
Even in a medium tank do not forget that Goldfish double in size every 6 months and so the excreta are doubled too.
You need a good filtration system to remove the ammonia, as well as via dilution.
Use a powered filter, internal or external, and do lots of partial water changes
to flush that toilet! About 10% weekly is OK, but occasional 50% is good for the
fish -
Note that, undergravel filters do not work! They are OK at tropical temperatures and with the small excreta of tropical fish, but the cooler water and copious excreta of Goldfish means the gravel gets filthy and putrifying bacteria develop instead of nitrifying species The bad bacteria spread onto the fish from the gravel and cause disease.
Do not overcrowd the tank, if you want many Goldfish, get a big tank to hold them. Water quality is everything for fish. Get the water quality right and the fish will be happy and happy fish are healthy fish. Goldfish should live 10 to 20 years in an aquarium (even 30 years in a pond).
Goldfish for Beginners
